Method of removing paint, varnish, and lacquer films from surfaces



United States Patent 1 2,704,278 METHOD OF REMOVING PAINT, VARNISH, AND LACQUER FILMS FROM SURFACES Harry R. Gamrath, St. Louis, Mo., assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Application June 7, 1950, Serial No. 166,774'

6 Claims. (Cl. 252-89) This invention relates to a method of removing paint, varnish and lacquer films from surfaces; more specifically, this invention relates to an improved method of removing paint, varnish and lacquer films from surfaces utilizing a composition containing an alkyl diaryl phosphate ester having the formula wherein R represents a radical selected from the group consisting of alkyl and alkoxyethyl radicals containing from 1 to 12 carbon atoms and R1 and R2 are each selected from the group consisting of phenyl and cresyl radicals.

The paint, varnish and lacquer removing compositions heretofore employed generally contained volatile and highly flammable organic solvents such as benzene, toluene and acetone which render the use of such compositions exceedingly hazardous from a flammability standpoint. It has been further found that the vapors which are evolved during the use of such compositions are frequently irritating to the mucous membrane, and the liquids contained in such compositions are frequently quite toxic, injurious to the skin and have disagreeable odors. These compositions also usually contain parafiin wax or other waxes for the purpose of retaining the volatile active ingredients on the painted surface during the paint softening operation. The subsequent removal of the softened paint from wood surfaces by scraping or other means tends to leave a residue of wax on the treated articles from which the coating is being removed. This wax film is not readily removable by water and frequently resists complete removal by means of gasoline, or a similar solvent. This wax residue is frequently responsible for poor adhesion of new paint subsequently applied to the surfaces. Moreover, the new paint film tends to stay sticky and to resist hardening in the presence of the wax film. When such compositions are utilized in removing paint from wood surfaces, it has been found that quite frequently a raising of the grain results.

One of the objects of this invention is to provide a method of removing paint, varnish and lacquer films from 2,704,278 Patented Mar. 15, 1955 surfaces utilizing a composition which is characterized by the absence of waxes and other normally solid or semisolid constituents.

Another object of this invention is to provide a method of removing paint, varnish and lacquer films from surfaces utilizing a composition characterized by non-toxicity and non-flammability thereby eliminating many of the hazards incidental to the paint removing compositions heretofore employed.

Further objects will become apparent from the description of the novel process of this invention.

It has now been discovered that paint, varnish and lacquer films may be softened in a relatively short time by applying thereto a composition containing one or more of the alkyl diaryl phosphate esters previously described. According to the novel process of this invention, therefore, paint, varnish and lacquer films are removed from a surface containing said films by applying thereto a composition containing one or more of these alkyl diaryl phosphate esters, allowing the composition to remain on the surface until the paint, varnish or lacquer film is loosened, and then removing the loosened film by suit able mechanical means, such as by scraping the surface with a scraping tool or by rubbing the surface with steel wool. After the paint, varnish or lacquer film has been removed from the surface, the residual composition containing the alkyl diaryl phosphate ester may then be removed quite readily from the surface by washing the treated area with water. Quite frequently the paint, varnish or lacquer film is so significantly loosened by treatment with the aforementioned compositions containing one or more of these alkyl diaryl phosphate esters, that flushing the surface with water is all that is required to completely remove the film. After the treated surface has dried, it may be repainted with full assurance that the resulting painted surface will dry properly and result in a hard, tack free surface.

The following examples are illustrative of the use of compositions containing an alkyl diaryl phosphate ester, as previously described, in removing paint, varnish and lacquer films:

Removal of paints from metal One side of a steel strip was covered with an aluminum paint while the other side was covered with a titaniumbase paint. A thin film of a composition containing an alkyl diaryl phosphate ester, as above described, was then applied to these strips and the effect of such compositions upon the painted surfaces noted. The results are indicated in Table A wherein are set forth the various compositions utilized and the time of contact between the composition and the painted surfaces necessary to permit a sufficient softening of the film to permit complete removal of the paint by mechanical means.

TABLE A.REMOVAL OF PAINTS FROM METALS Exposure Remarks Example Remover, Composition by Weight Thipsle, Remolyalaf Ea'mfi; with u y n 2'ethylhexyl diphenyl phosphate 50%. I {2-ethylhexyl dicresyl phosphate 50 0 Completely removed H {fi-methylhegtyl diphenyl phosphate, 50% 2 0 Do 3,5,5];tr1irf11ethylhtixylzll dipgletnyligmsphate, 50%...

met y ip eny p osp a e, HI ethyl diphenyl phosphate, 25%1." Iv butyl diphenyl phosphate, 90% 1 5 Do n-dodecyl diphenyl phosphate, 10%. V ethyl diphenyl phosphate, 70%. 1 5 DO tf ii li i t tFt-n11 -me yepy ipenypospae VI tetiraghloll'ogthglene, 5%.i1. t id .7.:..... 5

no ecy ip eny p osp a e VII grithllooeitlhyleile 75H..t .25.0.

uy 1p enypos ae o {99% 0p p n0l, 4o -l ggg g gggg gg g gggggg g;

. ter 2-ethy1hexyld1phenyl phosphate 607. wa 99%,sopmpan01 40 0 j Completely e ove 2ethylhexyldipl1enyl hos hat 1.5 Do. Z-ethylhexyldicresylp osp ate. 2.0 Do. methyl diphenyl phosphate 1.0 Do. ethyl diphenyl phosphate 1. 0 Do. fi-methylheptyl diphenyl hosphate-.. 1.5 Do. n-dodeeyl diphengl phosp ate... 2.5 Do. butyl diphenyl p1 osphate 1.0 Do. butoxyethyldi enyl hosphat 1.0 Do. benzoxyethyl ipheny phosphate. 4.0 Do.

Removal of points from wood Two varieties of samples were tested. One type is designated as red paint and the other as green paint. The wood strips covered with red paint had two coats of primer consisting of aluminum paint and one coat of red paint, the principal ingredient of the latter being iron oxide. The strips of wood covered with green paint had two coats of a white paint, the pigment being titanium oxide, and one coat of green paint, wherein the main pigment was lead chromate. Except for the titanium-base paint, the vehicle for the other paints was mainly an alkyd varnish.

A thin film of a composition containing an alkyl diaryl phosphate ester, as previously described, was applied to the painted surface of each of these wood strips. The composition was applied as indicated in Table B. The effect of these compositions upon the painted surface is set forth in Table B.

Alky! u'iaryl phosphate esters as brush softeners All of the paint brushes utilized in the following test contained pure pig bristles set in vulcanized rubber. To prepare the brushes for this test, the brushes were saturated with paint and the paint allowed to harden by aging.

TABLE B.REMOVAL OF PAINTS FROM WOOD Color Exposure Example of Test Remover, Composition by Weight gfigg Time, Remarks Board hrs.

(11.35 gsseitlally no1 astigln. in 2-ethylhexyl diphenyl phosphate, 507 4m move 0 um um primer I Red {2 ethy1hexy1dicresylphosphate, 2 }Brushed on-.. 3.0 Dgfiuiaiuyltktloifgemove aluminum paint with 6. Aluminum paint removed with steel wool. n-dodeoyl diphenyl phos hate 50 7 1: 0 H in-dodecyl dicresyl phosphate, 50%? same as above 0125 III do..-.- zethylhexyl phenyl cresyl phosphate, 100%- Cotton Wad..- ga Same as above.

4.0 1. 0 Paint tairly soit. butyl diphenyl phosphate, 50% i W do Brushed on.-. 1.6 Removed red slut with u knife.

{butoxyethyl diphenyl phosphate, 50% g t rem ig steel Wool.

. a y so V do methyl .dlphenyl phosphate 40% do 1. 5 Removed red paint with putty knife,

{butyl diphenyl phosphate 60% (5) Aluminum primer removed with steel wool.

butyl diphenyl phosphate, 907 VI {n-dodecyl dicresyl phosphate, 0% icotton Same as above 0. 25 Essentially no action. 2-ethylhexyl diphenyl phosphate, VII Green..- Brushed on..- 1. 0 Paint quite soft.

{aethylhexyl dicresyl phosphate, 50%... i 325 Down to wood Wm] putty me.

-dodeeyl diphenyl phosphate, 507 VIII {n-dodeeyl dicresyl phosphate, 50%1... same as above 0. 25 Essentially no action. IX do....- 2-ethylhexyl phenyl cresyl phosphate otton Wad... 21. (7)5 gonsitlletrgble S0ftfi1ng1ntwith m7 omp e remove 0 pa u lmiie. x do {butyl diphenyl phosphate, 50% }Bmshed on 1. 0 Most of paint removed. p

butoxyethyl diphenyl phosphate, 50%.. l. 5 Complete removal with putty knife. XI do {methyl diphenyl phosphate, 40% do 1. 0 Almost complete removal.

butyl diphenyl phosphate, 1. 5 Completeremovalotpalntwith puttylmlte. XII do {butyl diphenyl phosphate, 90%- }Comm wad 1. 0 Paint fairly soft.

"" n-dodeoyl dicresyl phosphate, 10'7 1. 5 Completeremoval of paintwith puttylmlie.

After removal of the painted surface in each of the tests described in Table B, each board was wiped vigorously with a cloth well soaked with turpentine. Then the board was wiped with a dry cloth and allowed to dry at room temperature. When dry, the boards were repainted. Half of these boards were given an undercoat of aluminum paint and the other half painted with a white paint (main pigmentcryptone). As a final coat, all boards were painted with a lead-base blue enamel. Drying of the enameled surface was satisfactory in all cases.

Removal of varnish from wood A 15-year old varnished surface was covered with a mixture of Z-ethylhexyl diphenyl phosphate and 2-ethylhexyl dicresyl phosphate (equal portions by weight). The phosphate ester mixture was applied with a brush.

After a few hours the surface was softened considerably. To show the non-volatile nature of the remover, the treated surface was allowed to stand for seven days after the first application of the ester. The syrupy mass was then removed with a putty knife thereby effecting a complete removal of the varnish film.

A 15-year old varnished surface was brushed with a 60:40% by weight mixture of tetrachloroethylene and ethyl diphenyl phosphate. After about One hour the var- Several paint formulas were used to saturate the brushes. These formulas were as follows:

Formula No. 1-Blaok enamel":

Pi m n giialrbondblaqk.

s an resins. vehlcle "{Volatile thinner. Formula No. 2-White paint":

Pigment 52.6%-

C to 82.0%.

Varnish 85.0 Drier and thinner 15.0 Formula No. 3-Blue enamel":

Pigment 42%- Sublimed lead [P102 10%. Vehicle 58% Tinted with Ultramarine Blue- Linseed oil 19.5%. ring 0 17.4%. Resins 12.8%. Japan drier 4.6%. Mineral spirits. 41.5%. Turpentine 4.2%. Formula No. 4-Laoquer Commercial linoleum lacquer. Formula No. 5Varnish":

Resins Vegetable 0118... 24%. Mineral spirits- 49%.

After the brushes had been thoroughly soaked in these Any of the alkyl diaryl phosphate esters having the formula i/ Roi wherein R represents a radical selected from the group TABLE 0,-ALKYL DIARYL PHOSPHATES AS BRUSH SOFTENERS Brush Paint Saturated Brush No. Formula Aged for Time Softening Agent, Composition by Weight Remarks Bruslti was (sloittfined in 18d hours, faslieil with 1 was Z-ethylhexyl diphenyl phosphate 50% an as 1 1 2 months" {2-ethylhexyl dicresyl phosphate, 230% g fig sg g? :33; gsggg gg gfigg gg asl 1A 2 do {2-ethylhexyl diphenyl hosphate, }Bru sh was softened and ready for washing r 2-ethylhexyl d cresyl p osphate, 50%. with water 111 2.5 hours. 2 2 1 week {Z-ethylhexyl drphenyl phosphate, 50% J[Brush was softened and ready for washing r t 2ethy1hexyl dicresyl phosphate, 50'? with water 1n 2.5 hours. 3 3 ca 2 months {n-dodecyl d phenyl phosphate, 50 Brush was softened and ready for washing n-dodecyl dicrgnyl phosphate, 50%. with water 1n 2.5 hours. 4 4 do {2-ethylbutyl d phenyl phosphate, 50 }Bru sh was softened and ready for washing t aethylb tyl cr v p p g g g s ready 0 m that r r treatment in 1 hour. Because varnish is methyl diphenyl phosphate, 75% 5 5 {ethyl dew phosphate, reass ss 52. 2.212. 2 assis ants: in turpentine and then washed with water.

The alkyl diaryl phosphate esters, as previously described, are characterized by low volatility and exceptionally low flammability. The physical properties of many of the phosphate esters which may be utilized in the novel process of this invention are set forth in Table D.

TABLE D.PHYSICAL PROPERTIES consisting of alkyl and alkoxyethyi radicals containing from 1 to 12 carbon atoms and R1 and R2 are each selected from the group consisting of phenyl and cresyl radicals may be utilized in the novel process of this invention. The alkyl and alkoxyethyl radicals as used in Ortho-Phosphate Ester N 0 Pour P oint,

Flash Point, 0 F.

2-Ethylhexyl dicresyl phosphate 2-E thylhexyl phenyl p-cresyl phosphate- G-Methylheptyl diphenyl phosphaten-Octyl diphenyl phosphate Benzoxyethyl diphenyl phosphate 3,5,5-trimethylhexyl diphenyl phosphate n-Deeyl diphenyl phosphate Z-Ethylhexoxyethyl phenyl cresyl phosphate. 1. 0795 n-Dodecyl diphenyl phosphate 1. 0402 n-Dodecyl dicresyl phosphate 1.025

In addition to these physical properties, these phosphate esters are characterized by low toxicity. The novel process of this invention, therefore, provides a means of removing paint, varnish and lacquer films wherein the toxicity and flammability hazards have been substantially eliminated. Due to the relatively low volatility of these alkyl diaryl phosphate esters, it is not necessary to employ any waxy materials in the paint removing compositions in order to retain the active ingredient on the painted surface during the paint softening operation. Utilizing the novel process of this invention, therefore, results in a wax-free surface.

As indicated in the preceding examples, the alkyl diaryl phosphate esters previously described may be utilized as the sole active ingredient in the paint removing composition or mixtures of various phosphate esters may be utilized. Furthermore, if desired, these phosphate esters may be mixed with other materials having some utility as paint removing ingredients. Typical of such additional agents which may be utilized are the various alkyl alcohols, trichloroethylene, tetrachloroethylene, etc. It is to be emphasized, however, that the use of such additional agents is not necessary for the purpose of this invention and, in fact, if used in too great a quantity, may detract from the desirable properties of the composition imparted thereto by these alkyl diaryl phosphate esters.

the above described formula, throughout the specification and in the claims, may be unsubstituted or substituted with one or more substituent radicals which do not deleteriously affect the desirable non-toxicity, stability, or non-corrosive properties of the particular phosphate ester. Typical of such substituent radicals are the hydroxyl radicals, alkoxyethoxy radicals, aryl radicals, such as the phenyl radical, and the substituted aryl radicals, such as the cresyl radical. These alkyl diaryl phosphate esters have been found to be particularly unique in the process of this invention as tricresyl phosphate or other liquid triaryl phosphates have been found to be ineffectual as paint removers because of their relatively slow softening action. Such triaryl phosphate esters are also considerably more toxic than the alkyl diaryl phosphate esters utilized in this process. Tri(2-ethylhexyl) phosphate has also been found to be essentially useless in such an application because of its exceptionally slow softening action. The lower trialkyl phosphates are too unstable hydrolytically, resulting in corrosion problems when their use in removing paint from metals is attempted.

The novel process of this invention has been found to be effective in the removal of aged paint, varnish, lacquer, enamel or resin films and newly applied or partially aged films. The process is applicable to the treatment of both metal and wood surfaces, as well as to the removal of paint, lacquer and varnish from other substances, for example, wool, cotton waste and textiles. Among the types of coatings removed from metal and wood surfaces by means of the novel process of this invention are those containing cellulose esters, such as cellulose nitrate and cellulose acetate; celluloseether, such as ethyl cellulose; phenol aldehyde resin coatings; varnishes including those containing rubber; paints formulated with white lead, barium sulfate, zinc sulfide or titanium oxide pigments and various oils, such as linseed oil, tung oil, oiticica oil and others; vinyl resin, melamine aldehyde rcsin, urea formaldehyde resin coatings, etc.

What is claimed is:

1. A process for the removal of paint, varnish and lacquer films from surfaces bearing said films comprising applying to said surfaces at film softening amount of a substantially non-inflammable fluent alkyl diaryl phosphate ester having the formula wherein R represents a radical selected from the group consisting of alkyl and alkoxyethyl radicals containing from 1 to 12 carbon atoms and R1 and R2 are each selected from the group consisting of phenyl and cresyl radicals, allowing said composition to remain on said surface until said film is loosened, and removing the loosened film.

2. A process as described in claim 1 wherein the alkyl diaryl phosphate ester is ethyl diphenyl phosphate.

3. A process as described in claim 1 wherein the alkyl diaryl phosphate ester is butyl diphenyl phosphate.

4. A process as described in claim 1 wherein the alkyl diaryl phosphate ester is butoxyethyl diphenyl phosphate.

5. A process as described in claim 1 wherein the alkyl diaryl phosphate ester is 2-ethylhexyl diphenyl phosphate.

6. A process as described in claim 1 wherein the alkyl diaryl phosphate ester is Z-ethylhexyl cresyl phenyl phosp ate.

References Cited in the file of this patent UNITED STATES PATENTS 1,499,101 Ellis June 24, 1924 1,938,714 Mills et a1. Dec. 12, 1933 2,005,619 Graves June 18, 1935 2,437,964 Marling Mar. 16, 1948 2,504,120 Gamrath Apr. 18, 1950 2,557,089 Gamrath et al June 19, 1951 

1. A PROCESS FOR THE REMOVAL OF PAINT, VARNISH AND LACQUER FILMS FROM SURFACES BEARING SAID FILMS COMPRISING APPLYING TO SAID SURFACE IN FILM SOFTENING AMOUNT OF A SUBSTANTIALLY NON-INFLAMMABLE FLUENT ALKYL DIARYL PHOSPHATE ESTER HAVING THE FORMULA 